Variable inertia drive mechanism



Aug. 29, 1967 P, STUDER 3,338,048

VARIABLE INERTIA DRIVE MECHANISM Original Filed Aug. 23, 1960 2Sheets-Sheet l INVENTOR Philip A. Sfudez;

1967 P. A. STUDE 3,338,048

VARIABLE INBRTIA DRIVE MECHANISM Original Filed Aug. 23, 1960 2Sheets-Sheet 2 m4 mgl 7/2 INVENTOR Philip A. Siudez;

United States Patent 3,338,048 VARIABLE INERTIA DRIVE MECHANISM PhilipA. Studer, Silver Spring, Md., assignor to Hamilton Watch Company,Lancaster, Pa., a corporation of Pennsylvania Continuation ofapplication Ser. No. 51,440, Aug. 23, 1960. This application Apr. 1,1964, Ser. No. 358,140 20 Claims. (Cl. 58-28) ABSTRACT OF THE DISCLOSUREDisclosed is a drive mechanism for oscillating systems in which kineticenergy is added to the system by changing the inertia of an oscillatingelement. An electromagnet is mounted on or adjacent the balance wheel ofa timepiece and is switched on and off in accordance with the rotaryposition of the balance wheel. The electromagnet moves a mass radiallyinward of the balance Wheel axis of rotation at or near the point ofmaximum velocity of the balance wheel and this mass is returned to itsinitial position at or near the point of zero velocity of the bal ancewheel. The changes in rotary moment of inertia of the oscillatingelements add net kinetic energy to drive the balance wheel.

This application is a continuation of copendin-g application Ser. No.51,440, filed Aug. 23, 1960.

This invention relates to a drive mechanism and more particularlyrelates to a variable inertia drive mechanism wherein a periodic changein inertia is used to restore the power consumed by friction in thedrive system and by any load that may be on the device.

Almost everyone interested in ice skating has seen a figure skaterperform a spin in which the arms are moved inwardly towards the skaterssides to increase the skaters speed of rotation and moved outwardly toslow it down. This increase in rotational velocity is caused by theoverall change in the moment of inertia of the skaters body and isillustrated in many high school and college physics classes by theprofessor having a student spin on a piano stool or similar rotatablesupport. The students speed of rotation, as with the ice skater, varieswith the inward and outward movement of the arms.

The physical principle underlying this action may in one sense beconsidered from the standpoint that the inward movement of the armsincreases the kinetic energy of the rotating body and that the skater orstudent must exert some effort, that is perform work, in order to movehis arms inwardly against the centrifugal forces of rotation tending tothrow his arms outwardly.

This principle has been used in the past as the basis of a governordevice for a continuously rotating shaft. Insofar as applicant is awareit has not been used as a drive for rotating elements, probably becauseof the fact that any energy imparted to a rotating element with a radialinward change in the moment of inertia of the rotating element isreturned upon outward movement as in the case of the skater and studentdescribed above, so that even neglecting losses the net energy impartedto the rotating element is zero.

The present invention is believed to provide for the first time acompletely inanimate arrangement, that is a mechanism independent of aliving creature, utilizing a change in rotational moment of inertia toincrease the kinetic energy of a mass so as to drive the mass andperform useful work. This is accomplished through the provision of anoscillating mass, and a device preferably in the form of anelectromagnet for changing the moment of inertia of the mass in adirection such as to increase its kinetic energy. Radial inward movementis most effective and least disturbing to the oscillations, particularlyif the oscillations are isochronal, if the inward movement occurs at thepoint of maximum angular velocity. Because an oscillating deviceundergoes a slowing down and stopping of movement as distinguished froma continuously rotating element such as a shaft, the mass of theoscillating device may be returned to its initial position or condition(its original moment of inertia) during a time when it is moving sloweror stopped, so that little or no energy is returned and the overalleffect is a net transfer of substantial energy into the oscillatingsystem.

A variable inertia drive mechanism constructed according to thisinvention may be used in a variety of ways. It may be used to drive awatch or clock, as a timing motor to drive a switching device, or it maybe used to drive an oscillating output shaft for numerous otherpurposes. If provided with a suitable converter the oscillating outputmay be converted into a unidirectional drive. Also the electromagneticnature of the preferred embodiment makes possible the utilization of thedevice as a source of accurately timed electrical impulses. The inertialdrive makes possible a relatively simple, inexpensive deviceparticularly suited for aerospace work. Additional advantages include asimpler and more reliable contact system, a standard coil form, and asymmetrical arrangement of components. In addition, if desired thecontact and consequently the drive pulse to the system can be made inboth directions of the wheels rotation rather than only once eachcomplete oscillation as employed in many previous asymmetrical watch andclock drives.

While the balance assembly of conventional timepieces is adapted toeffect isochronal oscillation of the balance wheel in each direction,energy lost through friction in both mechanically and electricallyoperated timepieces makes impossible the attainment of perfectisochronism. Since less than perfect isochronal oscillation of thebalance assembly results in imperfect timekeeping, this condition is notparticularly desirable.

It is accordingly a primary object of this invention to provide a noveldrive mechanism.

Another object of the invention is to provide a variable inertia drivemechanism.

Another object of the invention is to provide a mechanism for impartingenergy to oscillating systems by periodically changing the moment ofinertia of such systems.

Another object of the present invention is to provide novel balanceassemblies for a timepiece which have more perfect isochronal movementthan those of known timep1eces.

It is another object of the present invention to provide a noveltimepiece having a variable inertia drive mechanism in which anelectrical impulse is transformed into a change in inertia of anoscillating member.

It is another object of the invention to provide an electricallyoperated horological device with a greatly simplified contact orswitching mechanism system.

It is still another object of the invention to provide a constantfrequency signalling device in which a controlled change in inertia ofan oscillating body is used to maintain the constant frequency.

These and further objects and advantages of the present invention shallbecome more apparent upon reference to the following specification,claims and appended drawings wherein:

FIGURE 1 is a partially schematic, perspective view of the drivemechanism of the present invention, with parts broken away for purposesof clarity;

FIGURES 2 and 3 are top plan views of modified forms of the drivemechanism of FIGURE 1; and

FIGURE 4 is a sectional view taken through lines 4-4 in FIGURE 3.

As is clearly shown in FIGURE 1, the structure of one embodiment of thepresent invention comprises a balance wheel indicated generally at andcomposed of a two-piece split Tim, the rims beings indicated at 12 and14. Rims 12 and 14 are fixedly attached to opposite ends of a crossarmmember consisting of an upper spoke 16 and a lower spoke 18. Spokes 16and 18 are fixedly mounted for rotation with balance staff 20, which issupported in jewelled bearings (not shown) in the customary manner.

Rim 12 is provided with a bifurcated end 22, the upper furcation ofwhich is attached to one end of spoke 16, the lower furcation of whichis attached to spoke 18. Rim 14 is also provided with a bifurcated end24 (a portion of which is broken away for purposes of clarity), thefurcations of which are respectively secured to the other ends of spokes16 and 18. Rims 12 and 14 have tongued extensions 26 and 28,respectively, each of which extends between the furcations of thebifurcated end of the other rim.

Spokes 16 and 18 are recessed to receive the drive coils of a pair ofsolenoids 30 and 32 which are arranged in symmetrical relation withrespect to the balance staff 20. Each solenoid has a core member 34,only one of which is shown in the drawing. Each of core members 34 isfixedly attached to the adjacent tongued extension, one of said coremembers being shown to be attached at 36 to the tongued extension 26.

Upper spoke 16 carries a contact pin 38 which is insulated from thespoke by an insulating bushing 40. Contact pin 38 is adapted to beengaged by a fixed, elongated contact spring 42. Spring 42 is carried byan insulated post (not shown) in the frame of the assembly.

A collet 44 is fixedly attached to the balance staff for rotationtherewith. A flat wire torsion spring or hairspring 46 is inserted intoa slot in colle-t 44 as is customary in the watchmaking art, hairspring46 being adjustable to change its effective length in the usual mannerby means of a regulator (not shown).

A pair of insulated electrical leads 48 and 50 interconnect the contactpin 38 with each of the solenoids 30 and 32. The other ends of the coilsof solenoids 30 and 32 may electrically be connected through hairspring46 in' a conventional manner to complete an electrical circuit to anelectrical source such as battery 54 as shown schematically in thedrawing.

The operation of the foregoing embodiment of the variable inertia drivemechanism of the instant invention is as follows:

The balance wheel and staff assembly is turned to oscillate at a givenfrequency determined by the strength of hairspring 46 and the mass ofthe balance wheel assembly. Each time the balance wheel assembly passesthe neutral or rest position, insulated pin 38 strikes the fixedelongated contact spring 42, thereby completing the electrical circuitthrough the drive coils and pulling the solenoid core elements 34radially inwardly towards balance staff 20. In so doing, the moment ofinertia of the system about the staff is diminished and rotary motion ofthe entire assembly is accelerated. This results in an increase in theangular velocity of the balance wheel, which restores the energy lostdue to friction in the oscillation of the balance staff 20, and whateverenergy is given up to the load (i.e.,- the timepiece train) in the caseof the electric timepiece.

It will be understood that the shape or configuration of the crossarmsis immaterial and that while two elements have been shown, a singleelement may be used. A two element, skeletonized crossa-rm is preferredin order to minimize the mass of the rotating assembly and to thusaccentuate the change in inertia effected by moving the ends of the rimsinwardly.

Additional forms of variable inertia drive mechanisms, in which thedrive mechanism is in the form of fixed elec- 4 tromagnets separate fromthe oscillating balance assembly, are illustrated in FIGURES 24.

In the first of these, the mechanism illustrated in FIG- URE 2, abalance staff 60, mounted for oscillation in a conventional manner,supports -'a balance wheel indicated generally at 62 and having a hubportion 64, flexible spokes 66 and a rim 68. Rim '68 is constructed offerromagnetic material and, as illustrated, is divided into twosections, 70, and 72 each one of which is supported at its ends by twoflexible spokes 66. Hub portion '64 supports a contact post 74 which isadapted to engage a fixed flexible contact arm 76 during oscillation ofbalance wheel 62 in a conventional manner. A hairspring (not shown) isalso attached at one end to balance staff 60 in a known manner as in theembodiment of FIGURE 1.

The drive mechanism is equipped with two electromagnets 78 each havingtwo pieces 82 with arcuate surfaces 86 to conform to the curvature ofrim sections 70 and 72 of balance wheel 62. As may be seen in FIG- URE2, arcuate surfaces 86 of the electromagnets are spaced from butpositioned adjacent to the outer edge of rim sections 70 and 72.

Contact arm 76, contact post 74 and the electromagnet coils are placedin electrical communication with one another in the usual manner.

In essence, the operation of the structure illustrated in FIGURE 2 issimilar to that described above in connection with the structure shownin FIGURE 1. Rather than being drawn inwardly toward balance staff 60 atthe moment of energization of the electromagnets as was the case inconnection with the embodiment shown in FIG- URE 1, however, rimsections 70 and 72 are drawn outwardly at the moment of energization,flexible arms 66 permitting such outward movement as will be apparent.When the electromagnets are deenergized, the spring bias of flexiblearms 66 will induce rim sections 70 and 72 to return to their normalpositions and, as these sections move inwardly toward balance staff 60,the moment of inertia of the system about the staff will be diminishedas heretofore described and rotary motion of the entire assembly Will beaccelerated as before. This will again result in an increase in theangular velocity of the balance wheel, which will restore the energylost due to friction in the oscillation of the balance staff andwhatever energy is given up to the load.

Since it is desirable to induce the balance assembly to accelerate atthe point of greatest angular velocity, contact arm 76 and contact post74 should be positioned relative to one another so that energization ofthe electromagnets takes place at a point other than the neutral or restposition of the balance assembly, preferably at a point closer to theend limits of oscillation of the assembly. In this manner, rim sections70 and contact post 74 should-- be positioned relative to one another sothat energization of the electromagnets takes place at a point otherthan the neutral or rest position of the balance as sembly, preferablyat a point closer to the end limits of oscillation of the assembly. Inthis manner, rim sections 70 and 72 will, relatively speaking, be drawninwardly toward balance staff 60 as the assembly approaches its restposition and the effect in the variation in the moment of inertia of thesystem will be substantially identical to that described above inconnection with the system of FIG- URE 1.

If desired, of course, the system of FIGURE 1 could be modified tooperate similarly to that of FIGURE 2 by modifying the commutationsystem of the former in an obvious manner.

In the form of the invention illustrated in FIGURES 3 and 4, a structuresimilar to that shown in FIGURE 1 is utilized, including a two piece rim90 and 92 constructed of ferromagnetic material and cantilevered on acrossarm 94 which is suitably mounted for oscillation on a balance staff.96. Mounted -on crossarm 94 is a contact post 98 adapted to engage aflexible contact arm 100 during the oscillation of balance staff 96 inthe manner previously described. Balance staff 96 is also connected to ahairspring 102 in a conventional manner.

Connected in circuit with contact pin 98 and contact arm 100 in a knownmanner are two electromagnets 104, each of which has upstanding arms 108having convex sides 112 to conform to the configuration of the inside ofrim sections 90 and 92 as shown in FIGURE 3.

The operation of the'structure shown in FIGURES 3 and 4 does not differin essence from that described above in connection with the device inFIGURE 1. As the balance wheel assembly passes the neutral or restposition, insulated pin 98 strikes contact spring 100, completing theelectrical circuit through electromagnets 104 and p l rim sections 90and 92 inwardly toward balance staff 96. As before, the moment ofinertia of the system about the staff will be diminished and the angularvelocity of the balance wheel will increase to restore the energy lostdue to friction and to the load during the oscillation of the balancestaff.

The movable portions of the inertial assemblies described above do notnecessarily have to move sinusoidally as a simple spring mass system. Ifdesired, the residual magnetism of the system may be utilized to holdthe mass in the inward position for approximately one-quarter of anoscillation cycle, after which the rim sections would move rapidlyoutwardly at a point at which little or no energy would be lost to theoscillating system. Such an effect may be utilized either in the systemsillustrated in FIGURE 1 or in FIGURES 3 and 4.

It will be apparent that the variable inertia drive mechanisms of thepresent invention are extremely unique in their operation and provide atruly effective constant frequency source. While the devices will findtheir primary application in the timepiece field, they are equally wellsuited for use as signalling or triggering devices, or as mechanisms inwhich a constant frequency source is required; Thus, they may be used toprovide a source of timed electrical pulses, the electrical load beingplaced in series or in parallel with the solenoid drive coils.

The construction of the drive mechanisms is compact and easilyassembled. In addition, the switching means utilized in the instantdevices are much simpler than comparable means in currently availableelectric timepieces. The novel structures of the present invention alsoeffectively permit the use of a drive pulse in both directions ofoscillation of the balance assembly. In each of the embodimentsdisclosed oscillations may be initiated or started in any manner wellknown in the electric watch and clock fields such as by physicallyimpulsing or pushing the balance wheel, either manually (as by means ofa setting stem) or electrically (by means of a separate solenoid forthat purpose).

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States LettersPatent is:

1. A variable inertia drive mechanism comprising a rotatably mountedwheel, spring means coupled to said wheel whereby said wheel oscillatesbetween the maximum compressed and maximum expanded positions of saidspring means, an electromagnet having a radially movable core mounted onsaid wheel, and an electrical energizing circuit for said electromagnetincluding a movable contact carried by said wheel and a yieldablecontact in the path of movement of said movable contact.

2. A drive mechanism according to claim 1 wherein said contacts meet atthe neutral position of said spring means.

3. A variable inertia drive mechanism comprising a balance wheelrotatably mounted on a balance staff, a hairspring coupled to saidbalance staff, an electromagnet having a radially movable core mountedon said balance wheel, said core moving radially inward of said balancewheel when said electromagnet is energized to reduce the moment ofinertia of said balance wheel, and an electrical energization circuitfor said electromagnet including a movable contact carried by saidbalance wheel and a yieldable contact in the path of movement of saidmovable contact.

4. A variable inertia drive mechanism comprising a balance wheelrotatably mounted on a balance staff, a hairspring coupled to saidbalance staff, a pair of electromagnets symmetrically mounted on saidbalance wheel on opposite sides of said balance staff, each of saidelectromagnets having a core movable from a radial outward to a radailinward position with respect to said balance wheel when itselectromagnet is energized, spring means for returning each of saidcores to its radial outward position when said electromagnets aredeenergized, and means for energizing said electromagnets over at leastapproximately the last quarter of each oscillation of said balancewheel.

5. A drive according to claim 4 including means for energizing saidelectromagnets over approximately the last half of each half cycle ofsaid balance wheel.

6. A variable inertia drive mechanism comprising an oscillatable shaft;a crossarm member carried by said shaft; a first rim member attached atone end to one end of said crossarm member and free at its other end; asecond rim member attached to the other end of said crossarm member andfree at its other end; the free ends of said rim members beingsubstantially diametrically op posed; means carried by said crossarmmember engaging the free ends of said rim members to pull said free endsinwardly periodically during oscillation of said shaft to decrease themoment of inertia of said shaft-supported elements about said shaft; andmeans associated with said shaft for storing and releasing energyproduced by movement of said free ends inwardly thereby causing saidshaft to oscillate.

7. A variable inertia drive mechanism comprising an oscillatable shaft;a crossarm member carried by said shaft; a first arcuate rim memberattached at one end to one end of said crossarm member and free at itsother end; a second arcuate rim member attached to the other end of saidcrossarm member and free at its other end; the free ends of said arcuaterim member being substantially diametrically opposed; means carried bysaid crossarm member engaging the free ends of said arcuate rim members;switch means activating said free end-engaging means to pull said freeends inwardly each time said shaft oscillates through a rest position;and means associated with said shaft for storing and releasing energyproduced by movement of the ends of said arcuate rim when said solenoidsare energized thereby causing said shaft to oscillate.

8. A variable inertia drive mechanism as set out in claim 7 wherein saidswitch means com-prises an insulated contact pin carried by saidcrossarm member; a fixed elongated contact spring engageable with saidcontact pin; and means closing an electrical circuit upon engagement ofsaid contact pin and contact spring.

9. A variable inertia drive mechanism comprising an oscillatable shaft;a crossarm member carried by said shaft; an arcuate rim attached to eachend of said crossarm member; a pair of solenoids symmetrically supportedby said crossarm member; said solenoids having their core membersfixedly attached to the ends of each arcuate rim member opposite the endattached to said crossarm member; means to energize said solenoids eachtime said shaft oscillates through a rest position to move said coremembers inwardly toward said shaft; and means associated with said shaftfor storing and releasing energy pro duced by movement of the ends ofsaid arcuate rim when said solenoids are energized thereby causing saidshaft to oscillate.

10. A variable inertia drive mechanism as set out in claim 9 whereineach arcuate rim is bifurcated at the end attached to said crossarmmember and has a tongued end opposite said bifurcated end extending intothe bifurcated end of the other arcuate rim.

11. A variable inertia drive mechanism comprising an oscillatable shaft;a crossarm member carried by said shaft; a first rim member attached atone end to one end of said crossarm member and free at its other end; asecond rim mem-ber attached to the other end of said crossarm member andfree at its other end; the free ends of said rim members beingsubstantially diametrically opposed; means associated with said rimmembers for moving the free ends of said rim members inwardly towardssaid shaft over a portion of the angular path traversed by the shaftduring its oscillation; means for moving said free ends outwardly awayfrom said shaft over another portion of said angular path; inwardmovement of said free ends decreasing the moment of inertia of saidshaftsupported elements about said shaft; and means associated with saidshaft for storing and releasing energy produced by the movement of saidfirst and second masses thereby causing said shaft to oscillate.

12. A variable inertia drive mechanism comprising an oscillatable shaft;a rimmed member having first and second sections movable relative to oneanother and mounted on said shaft with said rim sections beingsubstantially symmetrically positioned relative to said shaft; meansassociated with said rim sections for moving them inwardly towards saidshaft over a portion of the angular path traversed by the shaft duringits oscillation; means for moving said rim sections outwardly away fromsaid shaft over another portion of said angular path; inward movement ofsaid rim sections decreasing the moment of inertia of saidshaft-supported elements about said shaft; and means associated withsaid shaft for storing and releasing energy produced by the movement ofsaid first and second masses thereby causing said shaft to oscillate.

13. A drive mechanism comprising a mass mounted for sustainedoscillatory movement, and means coupled to said mass for changing itsinertia at two predetermined spaced points in a cycle of oscillation,said means decreasing the inertia of said mass at a first point andincreasing the inertia of said mass at a second point of lesser velocitythan said first point whereby net kinetic energy is imparted to saidmass.

14. A drive mechanism according to claim 13 wherein said mass is mountedfor rotary oscillations, and said means changes the rotary moment ofinertia of said mass.

15. A drive mechanism comprising a mass mounted for sustained rotaryoscillations, said mass including electromagnetic means for changing itsrotary moment of inertia, and switch means coupled to said mass foractuating said electromagnetic means in accordance with the position ofsaid mass in the cycle of oscillation, said electromagnetic meansdecreasing the rotary moment of inertia of said mass when said mass isin a first position and increasing said rotary moment of inertia whensaid mass is in a second position, said second position being located ata point relative to said first position at which said mass possesses alesser angular velocity during a normal cycle of oscillation whereby netkinetic energy is imparted to said mass.

16. A drive mechanism according to claim 15 wherein said mass forms apart of a horological balance system.

17. A variable inertia drive system comprising a mass mounted for rotaryoscillations, resilient means coupled to said mass for sustainingoscillations of said mass, and means coupled to said mass for changingits rotary moment of inertia at two predetermined spaced points in acycle of oscillation, said means decreasing the rotary moment of inertiaof said mass at a first point and increasing the rotary moment ofinertia of said mass at a second point of lesser velocity than saidfirst point whereby net kinetic energy is imparted to said mass.

18. A drive mechanism according to claim 17 wherein said mass comprisesa balance wheel of a timepiece, and said resilient means is a springcoupled to said balance wheel.

19. A variable inertia drive mechanism comprising a body rotatablymounted for angular oscillating movement on a shaft, spring meanscoupled to said body for sustaining periodic'angular oscillations ofsaid body, a mass movably mounted on said body, and electromagneticmeans responsive to a predetermined position of said body for acting onsaid mass to move said mass radially of said shaft, said electromagneticme-ans moving said mass radially inward toward said shaft atapproximately the point of maximum angular velocity of said body, andmeans coupled to said body for returning said mass to its initialposition at approximately the point of zero velocity of said body.

20. A drive mechanism according to claim 19 including a pair of saidmasses equally spaced on diametrically opposite sides of the rotary axisof said shaft.

References Cited UNITED STATES PATENTS 203,623 5/187 8 Jay 74572 444,0811/ 1891 Wright 74-573 2,603,103 7/1952 Sohon et al. 74572 3,248,9675/1966 Lewis 74----572 MILTON O. HIRSHFIELD, Primary Examiner. v D. F.DUGGAN, Assistant Examiner.

17. A VARIBLE INERTIA DRIVE SYSTEM COMPRISING A MASS MOUNTED FOR ROTARYOSCILLATIONS, RESILIENT MEANS COUPLED TO SAID MASS FOR SUSTAININGOSCILLATIONS OF SAID MASS, AND MEANS COUPLED TO SAID MASS FOR CHANGINGITS ROTARY MOMENT OF INERTIA AT TWO PREDETERMINED SPACED POINTS IN ACYCLE OF OSCILLATION, SAID MEANS DECREASING THE ROTARY MOMENT OF INERTIAOF SAID MASS AT A FIRST POINT AND INCREASING THE ROTARY MOVEMENT OFINERTIA OF SAID MASS AT A SECOND POINT OF LESSER VELOCITY THAN SAIDFIRST POINT WHEREBY NET KINETIC ENERGY IS IMPARTED TO SAID MASS.
 18. ADRIVE MECHANISM ACCORDING TO CLAIM 17 WHEREIN SAID MASS COMPRISES ABALANCE WHEEL OF A TIMEPIECE, AND SAID RESILIENT MEANS IS A SPRINGCOUPLED TO SAID BALANCE WHEEL.